1. Field of the Invention
The present invention relates to a mechanism for coordinating the operation of carburetor throttle valves in a multi-cylinder internal combustion engine, for example.
2. Description of the Related Art
Conventional carburetors used in multi-cylinder internal combustion engines employ a mechanism similar to that shown in FIG. 3 to coordinate operation of the throttle valves. FIG. 3 is a plan view of the carburetor arrangement used in a V-type 4 cylinder internal combustion engine. Numeral 1 indicates the top edge of the internal combustion engine. Numeral 3 indicates the carburetors provided on top of each of the cylinders.
Numeral 4 indicates throttle valves. These throttle valves 4, are supported on shafts 5, arranged across the individual carburetors 3. The throttle valves 4 open and close with the rotation of the shafts 5. Also, adjacent pairs of carburetors 3 are arranged in series such that the shafts 5 are coaxial. Furthermore, these carburetors 3 are juxtaposed such that their shafts 5 are parallel to each other.
In the case of the above conventional carburetors 3, each shaft 5 is rotatably supported in bearings 6 provided on opposite ends thereof. Furthermore, the tips of adjacent shafts 5 protrude from the bearings 6, and are connected to each other by operation coordinating mechanisms 7a and 7b provided at the tips the of shafts 5. Also, to one of these shafts 5 (the lower right shaft in FIG. 3) is attached a drive mechanism 8. The rotation of this shaft (driving shaft) 5 is transmitted, via the link 9 extending between the tips of the shafts 5 protruding from the bearings 6, to the shafts 5 (driven shafts) of the carburetors 3 arranged in parallel to the carburetors on the driving side.
That is, in the conventional carburetor 3, when the shaft 5 in the lower right of the figure is rotated by the drive mechanism 8, the rotation is transmitted to the shaft 5 (the upper right shaft in the figure) by the operation coordinating mechanism 7a, and then to one of the driven shafts (the upper left shaft) 5 via the link 9, then by the operation coordinating mechanism 7b, to the shaft 5 (the lower left shaft). As a result, the shafts 5 rotate together by an equal amount, and open or close the throttle valves 4, thereby controlling the volume of air delivered to each of the cylinders.
However, in the above conventional throttle valve operation coordinating device, the link 9 extends between the tips of the shafts 5. Therefore, the link 9 is supported in a cantilever fashion by one end of the shaft 5. Particularly on the driven shafts 5, when rotation is transmitted through the link 9, the shaft 5 is pushed by the link 9 as shown by the arrow M in the figure, causing a swing left or right with the bearings 6 acting as a fulcrum. It is possible that the motion of the link 9 not be converted into the rotation of the shafts 5 correctly. Therefore, in the above conventional throttle valve operation coordinating device, to prevent the swing of the shafts 5 in the driven side carburetor 3 and the non-uniformity of the opening and closing amount and opening and closing time of the throttle valves 4 attached to them, despite the high cost, it is necessary to use bearings 6 to hold the shafts 5 firmly.